Conventional pumping machines that can be used for difficult-to-pump materials have displacement organs such as pistons, plungers, peristaltic hoses etc. However such displacement organs are subject to frictional wear and the drive of the machine is not properly isolated from the pumped material.
Pumps with flat or tubular diaphragms are known. A pump of the flat membrane type is commercialized by Geho. The tubular diaphragm pump is described as an improvement over the flat membrane type. One example of a tubular diaphragm pump is described in patent specification GB 2161221. This pump uses a flexible hose as diaphragm that is set in motion by an actuation fluid by means of a reciprocating piston, so that the diaphragm makes a movement comparable to a pulsating human vein. Hose diaphragm piston pumps are commercialized by Feluwa.
However the membranes of these known membrane pumps are driven by a crankshaft mechanism which especially in large machines is heavy and costly and requires pulsation dampening.
FR-A-315,900, Patent Abstracts of Japan 60008485, U.S. Pat. No. 2,464,095 and DE-A-1653445 all describe pumps in which pumped fluid and a pumping fluid are separated by a bellows-like diaphragm. However, none of the cited pump diaphragm systems possesses the advantage of a double protection of the pumped fluid from the pumping fluid, and none are adapted for multicylinder arrangements.